Stern Defense makes great AR magazine well adapters which turn your AR Lower into a Pistol Caliber Carbine. There are several models available which accept Glock magazines (9mm/.40), Beretta magazines (9mm) and two S&W M&P magazine versions in (9mm/.40 and .45 ACP). The latest version, the MAG-ADMP9&40/P320, uses both SIG P320 magazines and S&W M&P magazines.

These adapters are very sophisticated. They lock in hard with no wiggle after adjustment. They hold your mags in and drop them free. Unlike some other PCC’s, the bolt hold open works every time.

The .45 caliber adapter uses the excellent S&W M&P magazines.

With the gun ban scares over the last few years and the popularity of 80% lowers, most of you reading this have AR lowers in a closet that you never built. Here is the excuse to build the pistol caliber AR you always wanted. If you only have one AR, in one minute, you can change the upper, buffer and add a magazine well adapter. Boom, new gun.

If you have a registered full auto lower, Stern gives you caliber options. Short Barreled Rifle? Why not blast pistol ammunition? If you have a 9mm suppressor, there is no better host than a 9mm AR. These conversions provide more fun for your training dollar.

This excellent Stern Defense video shows the 9mm kit, installation and full auto firing. I have worked several AR conversions, but there is nothing quite like the Stern Defense system. I got their MAG-AD9 conversion kit, with adapter, complete 9mm caliber upper and their 11 ounce carbine buffer.

The Stern adapter fits snugly into the magazine well and adjust in three axes with Allen head screws. This is what plugs into your magwell. You can see the magazine release sticking out to the left. Photo courtesy of Stern.